Base modified oligonucleotides

ABSTRACT

The present invention relates to oligonucleotides with base modified nucleosides for enhancement of binding affinity.

This application claims priority to U.S. Provisional Application No.61/410,672, filed Nov. 5, 2010, which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to modified oligonucleotides with enhancedbinding affinity towards complementary polynucleotides.

BACKGROUND

MicroRNAs (miRs) have been implicated in a number of biologicalprocesses including regulation and maintenance of cardiac function (VanRooij et al., “MicroRNAs: Powerful New Regulators of Heart Disease andProactive Therapeutic Targets,” J. Clin, Invest. 117(9):2369-2376(2007); Chien K R, “Molecular Medicine: MicroRNAs and the Tell-taleHeart,” Nature 447:389-390 (2007)). Therefore, miRs represent arelatively new class of therapeutic targets for conditions such ascardiac hypertrophy, myocardial infarction, heart failure, vasculardamage, and pathologic cardiac fibrosis, among others. miRs are small,non-protein coding RNAs of about, 18 to about 25 nucleotides in length,and act as repressors of target mRNAs by promoting their degradation,when their sequences are perfectly complementary, or by inhibitingtranslation, when their sequences contain mismatches. The mechanisminvolves incorporation of the mature miRNA. strand into the RNA-inducedsilencing complex (RISC), where it associates with its target RNAs bybase-pair complementarity.

miRNA function may be targeted therapeutically by antisensepolynucleotides or by polynucleotides that mimic miRNA. function (“miRNAmimetic”). However, targeting miRNAs therapeutically witholigomieleotide-based agents poses several challenges, includingRNA-binding affinity and specificity, efficiency of cellular uptake, andnuclease resistance. For example, when polynucleotides are introducedinto intact cells they are attacked and degraded by nucleases leading toa loss of activity. While polynucleotide analogues have been prepared inan attempt to avoid their degradation, e.g., by means of 2′substitutions (Sproat et al, Nucleic Acids Research 17:3373-3386(1989)), the modifications often affect the polynucleotide's potency forits intended biological action. Such reduced potency, in each case, maybe due to an inability of the modified polynucleotide to form a stableduplex with the target RNA and/or a loss of interaction with thecellular machinery. Other modifications include the use of lockednucleic acid, which has the potential to improve RNA-binding affinity(Veedu et al., “Locked Nucleic Acid as a Novel Class of TherapeuticAgent,” RNA Biology 6:3, 321-323 (2009)).

Oligonucleotide chemistry patterns or motifs for miRNA inhibitors havethe potential to improve the delivery, stability, potency, specificity,and/or toxicity profile of the inhibitors, and as such are needed foreffectively targeting miRNA function in a therapeutic context.

SUMMARY OF THE INVENTION

The present invention relates to oligonucleotides comprising at leastone nucleotide having a 2′ modification and at least one nucleotidehaving an amino carbonyl modified base, as well as pharmaceuticalcompositions comprising the modified oligonucleotides, and methods ofuse and synthesis for these oligonucleotides.

In one aspect, the present invention provides oligonucleotidescomprising at least one nucleotide having a 2′ modification and at leastone nucleotide having an amino carbonyl modified base. In variousembodiments, the oligonucleotides provide advantages in duplex bindingaffinity, among other advantages, such as efficiency in RNA knockdown.In some embodiments, the oligonucleotide comprises a nucleotide sequencethat is at least substantially complementary to a nucleotide sequence ofhuman miRNA. In other embodiments, the oligonucleotide is at leastsubstantially complementary to a mammalian transcript, other than amiRNA, and is therefore useful for antisense inhibition of geneexpression. In still other embodiments, the oligonucleotide comprisesthe sequence of a human miRNA, and thereby mimics miRNA function. Instill other embodiments, the oligonucleotide is a detection probe for invitro detection or quantification of nucleic acids in a sample, usingany conventional platform.

The base modification is an amino carbonyl, such as a carboxamino,carbamoyl, or carbamide group. The modification in various embodimentsis at the C-5 position of a pyrimidine base or C-8 of a purine base. Themodifying amino carbonyl group of the instant oligonucleotide contains aradical or substituent which can be, without limitation, C-₁-C₁₈ alkyl,C₁-C₁₈ alkenyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, and—(CH₂)_(n)-NR₁R₂, wherein n is an integer from 1 to 6 and R₁ and R₂ areindependently H or C₁-C₆alkyl. Exemplary moieties include piperidine,piperazine, morpholino, or imidazole, each of which may be substitutedor unsubstituted. In other embodiments, the substituent is from C4 toC20 alkyl or alkenyl, phenyl, or an amine.

The oligonucleotide further comprises at least one nucleotide with a 2′modification. In some embodiments, the 2′ modifications may beindependently selected from C1-6 alkyl, 2′ O-alkyl(C1-C6), F, Cl, NH₂,CN, or SH. Other potential 2′ modifications are described elsewhereherein. An exemplary 2′ modification is 2′ O—Me, which may providesynergistic enhancements of the oligonucleotide's T_(m), together withthe base modification. In still other embodiments, at least, onenucleotide has a 2′ modification that is a 2′-4′ bridge locking thesugar in the C3 endo configuration. Unmodified 2′ positions may behydrogen.

The number of nucleotides having a modified base may vary, but incertain embodiments is at least 25% of nucleotides, or at least 50% ofnucleotides, or at least 75% of nucleotides or 100% of nucleotides. Insome embodiments, the enhancement of Tm may be accomplished withrelatively few base-modified nucleotides, such as less than 50% ofnucleotides or less than 25% of nucleotides. In some embodiments, theoligonucleotide contains only 1, 2, 3, or 4 base-modified nucleotides.The base modified nucleotides in these embodiments may be pyrimidinebases, such as uridine or thymine, and/or may contain a T modificationsuch as 2′ O'Me. That is, the oligonucleotide (e.g., of about16nucleotides) may have a single incorporation of a nucleotide havingthe base modification and 2′ OMe modification, with unmodified 2′positions being hydrogen, or alternatively independently selected fromLNA.

In certain embodiments, the oligonucleotide further comprises backbonechemistries such as cap modifications and phosphorothioate linkages.

The invention includes the discovery that novel base modified2′-OMe-pyrimidines show enhancements of duplex binding affinity withtheir complementary sequences when incorporated into antisenseoligonucleotides. Additionally, these pyrimidine base modified 2′-OMenucleotides with phosphorothioate backbone modifications show biologicalactivity against their microRNA target sequences in cell culture, evenwithout the use of transfection reagents. In vivo activity is alsodemonstrated herein using a model in vivo system showing knockdown oftarget iniRNA in cardiac tissue.

In another aspect, the present invention provides a method of reducingor inhibiting RNA expression or activity in a ceil, a method ofpreventing or treating a condition in a subject associated with ormediated by RNA or expression thereof, the method using the basemodified oligonucleotides described herein.

DESCRIPTION OF THE FIGURES

FIG. 1 is a table showing the amount of Tm enhancement for various basemodifications of 2′-OMe-uridine oligonucleotides. Base modificationswere carboxamido linkages at C5.

FIG. 2 illustrates the synthesis of modified monomelic nucleosides andcorresponding phosphoramidites for incorporation into oligonucleotides.

FIG. 3 illustrates hydrophilic and hydrophobic nucleoside modificationssynthesized via the scheme in FIG. 2 and shows some exampleincorporation patterns in oligonucleotides.

FIG. 4 compares Tm measurements for several base modifications againstLNA/DNA, 2′-OMe phoshorothioate, and DNA oligonucleotide. The basemodification pattern is shown.

FIG. 5 is a table of experimental Tm measurements for modifiedanti-miR-208a when duplexed with unmodified miR-208a RNA. Alloligonucleotides contain phosphorothioate linkages; +U stands for basemodified nucleotide with 2′ OMe; m stands for 2′ OMe, +U stands for C18base modification and 2′ OMe ribose; 1 stands for LNA modification; dstands for DNA.

FIG. 6 shows a miR-208a knockdown by modified antimiR-208a in ratprimary neonatal cardiomyocytes without lipid transfection reagent.

FIG. 7 shows the miR-208a knockdown data in FIG. 6 superimposed on bMFSClevels.

FIG. 8 is a plot of in vivo efficacy of base modified oligonucleotidesin C57BL/6mice. The plot shows the fold-change relative to salineinjections for some modified oligonucleotides.

FIG. 9 shows the cumulative effect of base and sugar modifications, withboth phosphate and phosphorothioate backbones.

FIG. 10 is a graph of ΔT_(m) against number of base modifications and 2′modifications, and shows the synergistic effect.

FIG. 11 is a graph of T_(m) effect of a select base modification withrespect to number of modifications and backbone chemistry.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to oligonucleotides comprising at leastone nucleotide having a 2′ modification and at least one nucleotidehaving an amino carbonyl modified base. The present invention furtherrelates to methods of use and synthesis for these oligonucleotides.

Studies of nucleoside base modification have been largely limited toinvestigations of effects on gene expression. Certain nucieobasederivatives, especially C-5 propynylated pyrimidines, have exhibitedonly modest gains in affinity/duplex stability for DNA/RNA duplexes(Znosko et al, J. Am. Chem. Soc., 125(20):6090-6097 2003)). More complexpendant functional groups (except as to known inter calators), areconsidered less likely to increase oligonucleotide affinity, given thepotential competing effects of hydrophobicity or steric effects(Hashimoto et al., J. Am. Chem. Soc., 115(16):7128-7134 (1993)).Similarly to sugar alterations, base modification may potentially changethe overall hydrophobicity and hydrogen bonding characteristic of anoligonucleotide bearing the modification, and might even lead tonon-canonical base pairing interactions (Vaught et al., J. Am. Chem.Soc., 132(12):4141-4151 (2010)), an effect that is not desirable forsequence-specific RNA inhibition.

In one aspect, the present invention provides oligonucleotidescomprising at least one nucleotide having a 2′ modification and at leastone nucleotide having an amino carbonyl modified base. In variousembodiments, the oligonucleotides provide advantages in duplex bindingaffinity, among other advantages, such as efficiency in RNA knockdown.

In some embodiments, the oligonucleotide comprises a nucleotide sequencethat is at least substantially complementary to a nucleotide sequence ofhuman miRNA. In. other embodiments, the oligonucleotide is substantiallycomplementary or fully complementary to a mammalian transcript, otherthan a miRNA, and is therefore useful for antisense inhibition of geneexpression. In still other embodiments, the oligonucleotide comprises asequence of a human miRNA sufficient to mimic of miRNA function. Inother embodiments, the oligonucleotide is a detection probe for in vitrodetection or quantification of nucleic acids in a sample, using anyconventional platform, such as a microarray or other hybridization-basedplatform.

In some embodiments, the oligonucleotide is from about 6 to about 22nucleotides in length. The oligonucleotides having one or more of thebase, sugar, and/or backbone modifications disclosed herein can be, forexample, from 8 to 18 nucleotides in length, or from 12 to 16nucleotides in length. In certain embodiments, the oligonucleotide isabout 8nucleotides in length, about 9 nucleotides in length, about 10nucleotides in length, about 11 nucleotides in length, about 12nucleotides in length, about 13 nucleotides in length, about 14nucleotides in length, about 15 nucleotides in length, or about 16nucleotides in length. For example, where the oligonucleotide targetsmiR-208a, the oligonucleotide may have the sequence CTTTTTGCTCGTCTTA(SEQ ID NO:64).

The base modification is generally an amino carbonyl, such as acarboxamino, carbamoyl, or carbamide group. The modification in variousembodiments is at the C-5position of one or more pyrimidine bases,and/or at C-8 of one or more purine bases. The modifying amino carbonylgroup of the instant oligonucleotide contains a radical or substituentwhich can be, without limitation, C₁-C₁₈ alkyl, C₁-C₁₈ alkenyl,cycloalkyl, aryl, heteroaryl, heterocyclyl, and —(CH₂)_(n)-NR₁R₂,wherein n is an integer from 1 to 6 and R₁ and R₂ are independently H orC₁-C₆alkyl.

For example, in some embodiments, the radical or substituent, is anitrogen-containing heterocyele, such as, for example, piperidine,piperazine, morpholino, or imidazole, each of which may be substitutedor unsubstituted with one, two, or three alkyl or alkenyl substituents(e.g., C1-8 or C1-4). Examples include 2-ethyl, 1-methyl-imidazole,3-propyl imidazole, and propyl morpholino, which are depicted in FIG. 1.In other embodiments, the radical or substituent is a carbocyclic group,such as a cycloalkyl (e.g., C5 to C8) or phenyl, which may optionally besubstituted with one or more (e.g., 1, 2, or 3) alkyl or alkenylsubstituents (e.g., C1-8 or C1-4). Examples include Benzyl as shown inFIG. 6. In still other embodiments, the radical or substituent is asecondary or tertiary amine, for example, having one or two alkyl oralkenyl substituents (e.g., C1-8, or C1-4). Examples include propyldimethyl amino, and ethyl dimethyl amino, as shown in FIG. 1. In someembodiments, the modifying amino carbonyl group contains a lipophilic orhydrophilic substituent, and in some embodiments, the substituent iscationic. Examples include C6 and C18 alkyl as shown in FIG. 1. In someembodiments, the radical or substituent is bound to the C5 position of apyrimidine base through a carboxamino linkage, optionally having alinking group of from 1 to 4 carbon units. The radical or substituentmay be as described elsewhere herein.

In some embodiments, the base modification contains a group that ispositively charged, and optionally having multiple positive charges,under physiological conditions, such as a pipirazine. Primary, secondaryand quaternary amines can also be used as suitable base modifications.In various embodiments, the base modification contains a peptidelinkage, which are more likely to be metabolized into less toxicnucleobases.

In some embodiments, the base modified nucleotides are incorporated inthe middle of the sequence. For example, in some embodiments, themodified nucleotides are not incorporated at the last 1, 2, or 3nucleotides on the 5′ and 3′ ends. Moieties that are cationic underphysiological conditions can provide substantial increases in T_(m).Notably, imidazole and morpholine derivatives that have pKa's in therange of 6.5-7.5 provide substantial binding and biological activity.Trialkylamines are also shown herein to be effective. Other cationicspecies of interest include guanidine type derivatives and hydrazines orhydroxylamines. Also of note are substituted piperazines, moieties thatoften act pharmacologically similar to morpholines due to similar pKa's,but that have two cationic centers. Hydrophobic substitutions such asbenzyl and alkyl moieties may also enhance T_(m), provide nucleaseresistance, and/or aid in cytosolic delivery.

In accordance with the present invention, the biological activity and Tmenhancement may be due in-part to an increase in. enthalpic binding, andtherefore, the modified oligonucleotides have the potential to enhancemismatch discrimination, and are thus useful as probes for diagnosticapplications.

The oligonucleotide further comprises at least one nucleotide with a 2′modification. As used herein, the term “2′ modification” includes any 2′group other than H or OH. For example, the 2′ modifications may beindependently selected from C1-6alkyl, 2′O-alkyl(C1-C6), F, Cl, NH2, CN,or SH. Other potential 2′ modifications are described elsewhere herein.An exemplary 2′ modification is 2′ O—Me, which may provide synergisticenhancements of the oligonucleotide's T_(m), together with the basemodification (e.g., when incorporated in the same nucleotide). In stillother embodiments, at least one nucleotide has a 2′ modification that isa 2′-4′ bridge locking the sugar in the C3 endo configuration.

In these or other embodiments, the oligonucleotide contains a 2′modification selected from alkyl, alkenyl, alkynyl, and alkoxyalkyl,where the alkyi (including the alkyl portion of alkoxy), alkenyl andalkynyl may be substituted or unsubstituted. The alkyl, alkenyl, andalkynyl may be C1 to C10 alkyl, alkenyl, or alkynyl, such as C1, C2, orC3, The hydrocarbon substituents may include one or two or threenon-carbon atoms, which may be independently selected from N, O, and/orS. The 2′ modifications may further include the alkyl, alkenyl, andalkynyl as O-alkyl, O-alkenyl, and O-alkynyl.

Other exemplary 2′ modifications in accordance with the inventioninclude 2′-O-alkyl (C1-3 alkyl, such as 2′OMe or 2′OEt),2′-O-methoxyethyl (2′-O-MOE), 2′-O-aminopropyl (2′-O-AP),2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl(2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyI (2′-O-DMAEOE), or2′-O-N-methylacetamido (2′-O-NMA) substitutions.

The oligonucleotide may have several nucleotides with the basemodification as described, such as from 1 to about 10, or about 2 toabout 9 nucleotides. In some embodiments, the oligonucleotide contains(exactly) 1, 2 or 3 nucleotides having the modified base. Theoligonucleotide may also, independently, have several nucleotidesmodified at the 2′ position. That is, the base modified nucleotides mayalso contain a 2′ modification as described, such as a 2′OMemodification. In some embodiments, at least one or two nucleotides haveboth a modified base and modified 2′ position, each as described above.In certain embodiments, the oligonucleotide comprises a nucleotide witha base modification shown in FIG. 1, together with a 2′OMe modification.The oligonucleotide in certain embodiments has exactly one, two, orthree of such modified nucleotides.

Where the 2′ modification is a 2′-4′ bridge, the 2′ modification may belocked nucleic acid (LNA). LNAs are described, for example, in U.S.Provisional Application Ser. No. 61/495,224, U.S. Pat. No. 6,268,490,U.S. Pat. No. 6,316,198, U.S. Pat. No. 6,403,566, U.S. Pat. No.6,770,748, U.S. Pat. No. 6,998,484, U.S. Pat. No. 6,670,461, and U.S.Pat. No. 7,034,133, all of which are hereby incorporated by reference intheir entireties. LNAs are modified nucleotides or ribonucleotides thatcontain an extra bridge between the 2′ and 4′ carbons of the ribosesugar moiety resulting in a “locked” conformation, and/or bicyclicstructure. In one embodiment, the oligonucleotide contains one or moreLNAs having the structure shown by structure A below. Alternatively orin addition, the oligonucleotide may contain one or more LNAs having thestructure shown by structure B below. Alternatively or in addition, theoligonucleotide contains one or more LNAs having the structure shown bystructure C below.

Other suitable locked nucleotides that can be incorporated in theoligonucleotides of the invention include those described in U.S. Pat.No. 6,403,566 and U.S. Pat. No. 6,833,361, both of which are herebyincorporated by reference in their entireties.

The oligonucleotide may contain at, least 3, at least 5, or at least 7locked nucleotides, and in various embodiments is not fully comprised oflocked nucleotides. In some embodiments, the number and position oflocked nucleotides may be as described in No. 61/495,224, which ishereby incorporated by reference, and particularly for miR-208 familyinhibitors.

The oligonucleotide may have one or more 2′ -deoxy nucleotides, and insome embodiments, contains from 2 to about 10 2′-deoxy nucleotides, insome embodiments, at least one, or all, base-modified nucleotides are 2′deoxy.

The number of nucleotides having a modified base may vary, but incertain embodiments is at least 25% of nucleotides, or at least 50% ofnucleotides, or at least 75% of nucleotides, or 100% of nucleotides. Asshown herein, the enhancement of T_(m) may be accomplished withrelatively few base-modified nucleotides, such as less than 50% ofnucleotides or less than 25% of nucleotides in some embodiments.However, in some embodiment, the oligonucleotide contains only 1, 2, 3,or 4 base-modified nucleotides (e.g., as shown in FIG. 1), and suchbase-modified nucleotides may also contain a 2′ modification such as 2′OMe. The base modified nucleotides in these embodiments may bepyrimidine bases, such as uridine or thymine in some embodiments. Insome embodiments, the oligonucleotide contains a single incorporation ofa base-modified oligonucleotide having a 2′ OMe.

In some embodiments, the oligonucleotide contains at least 6, or atleast 9 nucleotides having a 2′-OMe. Alternatively, all nucleotides (orall purines or all pyrimidines in some embodiments) may be 2′ O-Me.

The cationic class of C-5 modified bases exhibited substantial Tmenhancement (as shown herein), in addition to some lipophilicenhancements to the C-5 position of 2′-OMe-Uridine. Beyond simpleWatson-Crick base pairing to miRNA's of interest, mixtures ofmodifications containing both lipophilic and cationic moieties may havea larger effect on miRNA's already associated with intracellular enzymesand proteins that regulate the miRNA's activity. These chimericnucleotides may not only associate with their complementary targetsequence, but also interact with hydrophobic or hydrophilic regions ofthe protein associated with the miRNA.

In certain embodiments, the oligonucleotide further comprises at leastone terminal modification or “cap”. The cap may be a 5′ and/or a 3′-capstructure. The terms “cap” or “end-cap” include chemical modificationsat either terminus of the oligonucleotide (with respect to terminalribonucleotides), and including modifications at the linkage between thelast two nucleotides on the 5′ end and the last two nucleotides on the3′ end. The cap structure as described herein may increase resistance ofthe oligonucleotide to exonucleases without compromising molecularinteractions with the RNA target or cellular machinery. Suchmodifications may be selected on the basis of their increased potency invitro or in vivo. The cap can be present at the 5′-terminus (5′-cap) orat the 3′-terminus (3′-cap) or can be present on both ends. In certainembodiments, the 5′- and/or 3′-cap is independently selected fromphosphorothioate monophosphate, abasic residue (moiety),phosphorothioate linkage, 4′-thio nucleotide, carbocyclic nucleotide,phosphorodithioate linkage, inverted nucleotide or inverted abasicmoiety (2′-3′ or 3′-3′), phosphorodithioate monophosphate, andmethylphosphonate moiety. The phosphorothioate or phosphorodithioateImkage(s), when part of a cap structure, are generally positionedbetween the two terminal nucleotides on the 5′ end and the two terminalnucleotides on the 3′ end.

In certain embodiments, the oligonucleotide has at, least one terminalphosphorothioate monophosphate. The phosphorothioate monophosphate maybe at the 5′ and/or 3′ end of the oligonucleotide. A phosphorothioatemonophosphate is defined by the following structures, where B is base,and R is a 2′ modification as described above:

Phosphorothioate linkages may be present in some embodiments, such asbetween the last two nucleotides on the 5′ and the 3′ end (e.g., as partof a cap structure), or as alternating with phosphodiester bonds. Inthese or other embodiments, the oligonucleotide may contain at least oneterminal abasic residue at either or both the 5′ and 3′ ends. An abasicmoiety does not contain a commonly recognized purine or pyrimidinenucleotide base, such as adenosine, guanine, cytosine, uracil orthymine. Thus, such abasic moieties lack a nucleotide base or have othernon-nucleotide base chemical groups at the 1′ position. For example, theabasic nucleotide may be a reverse abasic nucleotide, e.g., where areverse abasic phosphoramidite is coupled via a 5′ amidite (instead of3′ amidite) resulting in a 5′-5′ phosphate bond. The structure of areverse abasic nucleoside for the 5′ and the 3′ end of a polynucleotideis shown below.

The oligonucleotide may contain one or more phosphorothioate linkages.Phosphorothioate linkages have been used to render oligonucleotides moreresistant to nuclease cleavage. For example, the polynucleotide may bepartially phosphorothioate-linked, for example, phosphorothioatelinkages may alternate with phophodiester linkages. In certainembodiments, however, the oligonucleotide is fullyphosphorothioate-linked. In other embodiments, the oligonucleotide hasfrom one to five or one to three phosphate linkages.

The synthesis of oligonucleotides, including modified polynucleotides,by solid phase synthesis is well known and is reviewed by Caruthers etal., “New Chemical Methods for Synthesizing Polynucleotides,” NucleicAcids Symp. Ser., (7):215-23 (1980) which is hereby incorporated byreference in its entirety.

The invention includes the discovery that novel base modified2′-OMe-pyrimidines show enhancements of duplex binding affinity withtheir complementary sequences when incorporated into 2′-OMe nucleotides(See FIG. 1). Additionally, these pyrrolidine base modified 2′-OMenucleotides with phosphorothioate backbone modifications show biologicalactivity against their microRNA. target, sequences in cell culture, evenwithout the use of transfection reagents, a characteristic thatunconjugated 2′-OMe phosphorothioate nucleotides do not exhibit withoutthe use of special 3′ and 5′-conjugates. Further, as shown herein,pyrimidine base modified 2′-OMe nucleotides with phosphorothioatebackbone modifications exhibit knockdown of target miRNA in cardiactissue following saline injection (FIG. 8).

A series of model compounds were synthesized where the pendantmodification on the C-5 base position were either hydrophobic orhydrophilic. Structures are included in FIGS. 1-3. Anti-miRNAoligonucleotides containing only C-5 hydrophobic modifications of all ofthe 2′-OMe-uridine nucleosides, modestly increases the T_(m) of a duplexcompared to the nucleotides with unmodified 2′-OMe-uridine. Thesenucleotides did not provide substantial benefit with respect to miRNAinhibition in cell culture experiments, both with and without lipidtransfection reagents (FIGS. 6 and 7). In contrast, anti-miRNAnucleotides containing hydrophilic, amine (cationic) containing pendant,groups alone on C-5 of all uridines showed large increases in T_(m)(FIGS. 4-6). Furthermore, cell culture experiments with nucleotidescontaining these modifications show unique biological properties such asthe ability to inhibit, miRNA. targets, even in the absence of lipidtransfection reagents or conjugates. It should also be noted that somenucleotides with combinations of hydrophobic and cationic basemodifications showed good anti-miRNA activity.

Without being bound by theory, it is believed that these pyrimidine basemodifications enhance binding affinity through interaction with thepolar major groove of the resulting RNA. duplexes. The nucleosidesdescribed herein are modified, for example, via carboxamidomodifications that are cross conjugated to the pyrimidine base andprovide additional hydrogen bonding sites, either to another nucleobaseor to the polar major groove. This is a distinct mode of duplexstabilization than commonly used sugar modifications, such as bridgednucleosides and 2′-modifications, that favor A-form conformations of thenucleobase which enhance binding to RNA. Therefore, it is believed thatthese C-5 carboxamido-modified nucleobases will act at least additivelyto the binding enhancement provided by sugar modification. C-5carboxamido-modified nucleosides that also contain a 2′-4′-bridged sugarcan also be employed to achieve enhanced binding of the oligonucleotidesto their target, including the bridge structure shown below.Oligonucleotides incorporating the 2′-CBBN nucleosides are described inU.S. Provisional Application No. 61/532,738, which is herebyincorporated by reference. As shown in the structure below, R representsthe carboxamido modification described herein, and R′ and R″ representthe 5′ and 3′ ends.

The carboxamido-modifications of the C-5 position of uridine, and thechemistry and stabilization characteristics, can be extended to thecytidine base. Similar modifications can be employed for purine basesvia carboxamido-type modifications described herein.

Nucleotides incorporating the modified nucleobases described hereindisplay enhanced binding affinity to their complementary nucleotides.Increases in Tm have been measured as high as 5° C./incorporation (FIG.5), comparable to the bicyciic LNA monomers that, to this point, havebeen observed to be the most effective and widely used affinityenhancing modification. The enhancement of T_(m) may be especiallyeffective in creating more active and potent microRNA inhibitors.Additionally, some of these new nucleobase modifications likely enhancecellular uptake by either masking some of the negatively chargedphosphates, in the case of cationic moieties, or, in the case oflipophilic modifications, by shielding the backbone from nucleases andcreating an amphiphiliic nucleotide (FIGS. 6, 7, and 8).

The modifications may be used in oligonucleotides designed to mimicmiRNA sequences, and may comprise any one of the mature miRNA sequencesin Table 1 below. Such antisense and sense sequences may be incorporatedinto shRNAs or other RNA structures containing stem and loop portions,for example. Such sequences are useful for, among other things,mimicking or targeting miRNA function for treatment or amelioratingcardiac hypertrophy, myocardial infarction, heart failure (e.g.,congestive heart failure), vascular damage, and/or pathologic cardiacfibrosis, among others. Exemplary miRNA therapeutic utilities aredisclosed in the US and PCT patent references listed in Table 1below,each of which is hereby incorporated by reference in its entirety. Themature and pre-processed forms of miRNAs are disclosed in the patentreferences listed below, and such descriptions are also herebyincorporated by reference.

TABLE 1 miRNA miRNA Sequence Reference   1UGGAAUGUAAAGAAGUAUGUAU (SEQ ID No. 1) WO 2009/012468 100AACCCGUAGAUCCGAACUUGUG (SEQ ID No. 2) WO 2009/012468  10bUACCUGUAGAACCGAAUUUGUG (SEQ ID No. 3) WO 2009/012468 125bUCCCUGAGACCCUAACUUGUGA (SEQ ID No. 4) WO 2009/012468 128UCACAGUGAACCGGUCUCUUU (SEQ ID No. 5) WO 2007/070483 133aUUUGGUCCCCCUUCAACCAGCUG (SEQ ID No. 6) WO 2009/012468 133bUUUGGUCCCCUUCAACCAGCUA (SEQ ID No. 7) WO 2009/012468 139UCUACAGUGCACGUGUCUCCAG (SEQ ID No. 8) WO 2009/012468 143UGAGAUGAAGCACUGUAGCUC (SEQ ID No. 9) WO 2007/070483 145GUCCAGUUUUCCCAGGAAUCCCU (SEQ ID No. 10) WO 2007/070483 150UCUCCCAACCCUUGUACCAGUG (SEQ ID No. 11) WO 2009/012468  15aUAGCAGCACAUAAUGGUUUGUG (SEQ ID No. 12) WO 2009/062169  15bUAGCAGCACAUCAUGGUUUACA (SEQ ID No. 13) WO 2009/062169  16UAGCAGCACGUAAAUAUUGGCG (SEQ ID No. 14) WO 2009/062169 181bAACAUUCAUUGCUGUCGGUGGGU (SEQ ID No. 15) WO 2009/012468 195UAGCAGCACAGAAAUAUUGGC (SEQ ID No. 16) WO 2009/012468 197UUCACCACCUUCUCCACCCAGC (SEQ ID No. 17) WO 2009/012468 199aCCCAGUGUUCAGACUACCUGUUC (SEQ ID No. 18) WO 2009/012468 199B miR-199b-5pUS 61/047,005 CCCAGUGUUUAGACUAUCUGUUC (SEQ ID No. 19) miR-199b-3pACAGUAGUCUGCACAUUGGUUA (SEQ ID No. 20) 206UGGAAUGUAAGGAAGUGUGUGG (SEQ ID No. 21) WO 2007/070483 208aAUAAGACGAGCAAAAAGCUUGU (SEQ ID No. 22) WO 2008/016924 208bAUAAGACGAACAAAAGGUUUGU (SEQ ID No. 23) WO 2009/018492 20aUAAAGUGCUUAUAGUGCAGGUAG (SEQ ID No. 24) US 60/950,565  21UAGCUUAUCAGACUGAUGUUGA (SEQ ID No. 25) WO 2009/058818 214ACAGCAGGCACAGACAGGCAGU (SEQ ID No. 26) US 61/047,005  22AAGCUGCCAGUUGAAGAACUGU (SEQ ID No 27) WO 2009/012468 221AGCUACAUUGUCUGCUGGGUUUC (SEQ ID No. 28) WO 2009/012468 222AGCUACAUCUGGCUACUGGGU (SEQ ID No. 29) WO 2009/012468 224CAAGUCACUAGUGGUUCCGUU (SEQ ID No. 30) WO 2009/012468  23aAUCACAUUGCCAGGGAUUUCC (SEQ ID No. 31) WO 2009/012468  26aUUCAAGUAAUCCAGGAUAGGCU (SEQ ID No. 32) WO 2007/070483  26bUUCAAGUAAUUCAGGAUAGGU (SEQ ID No. 33) WO 2009/012468  28AAGGAGCUCACAGUCUAUUGAG (SEQ ID No. 34) WO 2009/012468  29aUAGCACCAUCUGAAAUCGGUUA (SEQ ID No. 35) WO 2009/018493  29bUAGCACCAUUUGAAAUCAGUGUU (SEQ ID No. 36) WO 2009/018493  29cUAGCACCAUUUGAAAUCGGUUA (SEQ ID No. 37) WO 2009/018493  30aUGUAAACAUCCUCGACUGGAAG (SEQ ID No. 38) PCT/US2010/031147  30bUGUAAACAUCCUACACUCAGCU (SEQ ID No. 39) PCT/US2010/031147  30cUGUAAACAUCCUACACUCUCAGC (SEQ ID No. 40) WO 2009/012468  30dUGUAAACAUCCCCGACUGGAAG (SEQ ID No. 41) PCT/US2010/031147  30eUGUAAACAUCCUUGACUGGAAG (SEQ ID No. 42) PCT/US2010/031147 342-3pUCUCACACAGAAAUCGCACCCGU (SEQ ID No. 43) WO 2009/012468 382GAAGUUGUUCGUGGUGGAUUCG (SEQ ID No. 44) WO 2009/012468 422aACUGGACUUAGGGUCAGAAGGC (SEQ ID No. 45) US 2009/0226375 378ACUGGACUUGGAGUCAGAAGG (SEQ ID No. 46) WO 2009/012468 424CAGCAGCAAUUCAUGUUUUGAA (SEQ ID No. 47) WO 2009/062169 483-3pUCACUCCUCUCCUCCCGUCUU (SEQ ID No. 48) WO 2009/012468 484UCAGGCUCAGUCCCCUCCCGAU (SEQ ID No. 49) WO 2009/012468 486-5pUCCUGUACUGAGCUGCCCCGAG (SEQ ID No. 50) WO 2009/012468 497CAGCAGCACACUGUGGUUUGU (SEQ ID No. 51) WO 2009/062169 499UUAAGACUUGCAGUGAUGUUU (SEQ ID No. 52) WO 2009/018492 542-5pUCGGGGAUCAUCAUCACGAGA (SEQ ID No. 53) WO 2009/012468  92aUAUUGCACUUGUCCCGGCCUGU(SEQ ID No. 54) WO 2009/012468  92bUAUUGCACUCGUCCCGGCCUCC (SEQ ID No. 55) WO 2009/012468 let-7aUGAGGUAGUAGGUUGUAUAGUU (SEQ ID No. 56) WO 2009/012468 let-7b UGAGGUAGUAGGUUGUGUGGUU (SEQ ID No. 57) WO 2009/012468 let-7cUGAGGUAGUAGGUUGUAUGGUU (SEQ ID No. 58) WO 2009/012468 1et-7dAGAGGUAGUAGGUUGCAUAGUU (SEQ ID No. 59) WO 2009/012468 1et-7eUGAGGUAGGAGGUUGUAUAGUU (SEQ ID No. 60) WO 2009/012468 let-7fUGAGGUAGUAGAUUGUAUAGUU (SEQ ID No. 61) WO 2009/012468 let-7gUGAGGUAGUAGUUUGUACAGUU (SEQ ID No. 62) WO 2009/012468 451AAACCGUUACCAUUACUGAGUU (SEQ ID No. 63) PCT/US2010/034227

In some embodiments, the oligonucleotide targets a miR-208 family miRNA,such as miR-208a or miR-2()8b, or alternatively miR-15b or miR-21. Insome embodiments, the oligonucleotide has a sequence and structure shownin FIG. 5. “m” refers to 2′ OMe modification, and “+” refers tobase-modified nucleotide with 2′ OMe, Descriptions of abbreviations arefound in FIG. 1 and FIG. 5.

The oligonucleotide may be incorporated within a variety ofmacromolecular assemblies or compositions. Such complexes for deliverymay include a variety of liposomes, nanoparticles, and micelles,formulated for delivery to a patient. The complexes may include one ormore fusogenic or lipophilic molecules to initiate cellular membranepenetration. Such molecules are described, for example, in U.S. Pat. No.7,404,969 and U.S. Pat. No. 7,202,227, which are hereby incorporated byreference in their entireties. Alternatively, the oligonucelotide mayfurther comprise a pendant lipophilic group to aid cellular delivery,such as those described in WO 2010/129672, which is hereby incorporatedby reference.

In another aspect, the present invention relates to a pharmaceuticalcomposition which comprises an effective amount of the oligonucleotideof the present invention or a its pharmaceutically-acceptable, and apharmaceutically-acceptable carrier or diluent.

The composition or formulation may employ a plurality of therapeuticoligonucleotides, including at least one described herein. For example,the composition or formulation may employ at least 2, 3, 4, or 5 miRNAinhibitors described herein.

The oligonucleotides of the invention may be formulated as a variety ofpharmaceutical compositions. Pharmaceutical compositions will beprepared in a form appropriate for the intended application. Generally,this will entail preparing compositions that are essentially free ofpyrogens, as well as other impurities that could be harmful to humans oranimals. Exemplary delivery/formulation systems include colloidaldispersion systems, macro-molecule complexes, nanocapsules,microspheres, beads, and lipid-based systems including oil-in-wateremulsions, micelles, mixed micelles, and liposomes. Commerciallyavailable fat emulsions that are suitable for delivering the nucleicacids of the invention to cardiac and skeletal muscle tissues includeIntralipid®, Liposyn®, Liposyn® II, Liposyn(r) III, Nutrilipid, andother similar lipid emulsions. A preferred colloidal system for use as adelivery vehicle in vivo is a liposome (i.e., an artificial membranevesicle). The preparation and use of such systems is well known in theart. Exemplary formulations are also disclosed in U.S. Pat. No.5,981,505; U.S. Pat. No. 6,217,900; U.S. Pat. No. 6,383,512; U.S. Pat.No. 5,783,565; U.S. Pat. No. 7,202,227; U.S. Pat. No. 6,379,965; U.S.Pat. No. 6,127,170; U.S. Pat. No. 5,837,533; U.S. Pat. No. 6,747,014;and WO03/093449, which are hereby incorporated by reference in theirentireties.

The pharmaceutical compositions and formulations may employ appropriatesalts and buffers to render delivery vehicles stable and allow foruptake by target cells. Aqueous compositions of the present inventioncomprise an effective amount of the delivery vehicle comprising theinhibitor oligonucleotide (e.g. liposomes or other complexes), dissolvedor dispersed in a pharmaceutically acceptable carrier or aqueous medium.The phrases “pharmaceutically acceptable” or “pharmacologicallyacceptable” refers to molecular entities and compositions that do notproduce adverse, allergic, or other untoward reactions when administeredto an animal or a human. As used herein, “pharmaceutically acceptablecarrier” may include one or more solvents, buffers, solutions,dispersion media, coatings, antibacterial and antifungal agents,isotonic and absorption delaying agents and the like acceptable for usein formulating pharmaceuticals, such as pharmaceuticals suitable foradministration to humans. The use of such media and agents forpharmaceutically active substances is well known in the art.Supplementary active ingredients also can be incorporated into thecompositions.

Administration or delivery of the pharmaceutical compositions accordingto the present invention may be via any route so long as the targettissue is available via that route. For example, administration may beby intradermal, subcutaneous, intramuscular, intraperitoneal orintravenous injection, or by direct injection into target tissue (e.g.,cardiac tissue). The stability and/or potency of the oligonucleotidesdisclosed herein allows for convenient routes of administration,including subcutaneous, intradermal, and intramuscular. Pharmaceuticalcompositions comprising miRNA inhibitors may also be administered bycatheter systems or systems that isolate coronary circulation fordelivering therapeutic agents to the heart. Various catheter systems fordelivering therapeutic agents to the heart and coronary vasculature areknown in the art. Some non-limiting examples of catheter-based deliverymethods or coronary isolation methods suitable for use in the presentinvention are disclosed in U.S. Pat. No. 6,416,510; U.S. Pat. No.6,716,196; U.S. Pat. No. 6,953,466, WO 2005/082440, WO 2006/089340, U.S.Patent Publication No. 2007/0203445, U.S. Patent Publication No.2006/0148742, and U.S. Patent Publication No. 2007/0060907, which areall hereby incorporated by reference in their entireties.

The compositions or formulations may also be administered parenterallyor intraperitoneally. By way of illustration, solutions of theconjugates as free base or pharmacologically acceptable salts can beprepared in water suitably mixed with a surfactant, such ashydroxypropylcellulose. Dispersions can also be prepared in glycerol,liquid polyethylene glycols, and mixtures thereof and in oils. Underordinary conditions of storage and use, these preparations generallycontain a preservative to prevent the growth of microorganisms.

The pharmaceutical forms suitable for injectable use or catheterdelivery include, for example, sterile aqueous solutions or dispersionsand sterile powders for the extemporaneous preparation of sterileinjectable solutions or dispersions. Generally, these preparations aresterile and fluid to the extent that easy injectability exists.Preparations should be stable under the conditions of manufacture andstorage and should be preserved against the contaminating action ofmicroorganisms, such as bacteria and fungi. Appropriate solvents ordispersion media may contain, for example, water, ethanol, polyol (forexample, glycerol, propylene glycol, and liquid polyethylene glycol, andthe like), suitable mixtures thereof, and vegetable oils. The properfluidity can be maintained, for example, by the use of a coating, suchas lecithin, by the maintenance of the required particle size in thecase of dispersion and by the use of surfactants. The prevention of theaction of microorganisms can be brought about by various antibacterialan antifungal agents, for example, parabens, chlorobutanol, phenol,sorbic acid, thimerosal, and the like. In many cases, it will bepreferable to include isotonic agents, for example, sugars or sodiumchloride. Prolonged absorption of the injectable compositions can bebrought about by the use in the compositions of agents delayingabsorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions may be prepared by incorporating theconjugates in an appropriate amount into a solvent along with any otheringredients (for example as enumerated above) as desired. Generally,dispersions are prepared by incorporating the various sterilized activeingredients into a sterile vehicle which contains the basic dispersionmedium and the desired other ingredients, e.g., as enumerated above. Inthe case of sterile powders for the preparation of sterile injectablesolutions, the preferred methods of preparation include vacuum-dryingand freeze-drying techniques which yield a powder of the activeingredients) plus any additional desired ingredient from, a previouslysterile-filtered solution thereof.

Upon formulation, solutions are preferably administered in a mannercompatible with the dosage formulation and in such amount as istherapeutically effective. The formulations may easily be administeredin a variety of dosage forms such as injectable solutions, drug releasecapsules and the like. For parenteral administration in an aqueoussolution, for example, the solution generally is suitably buffered andthe liquid diluent first rendered isotonic for example with sufficientsaline or glucose. Such aqueous solutions may be used, for example, forintravenous, intramuscular, subcutaneous and intraperitonealadministration. Preferably, sterile aqueous media are employed as isknown to those of skill in the art, particularly in light of the presentdisclosure. By way of illustration, a single dose may be dissolved in 1ml of isotonic NaCl solution and either added to 1000 ml ofhypodermoclysis fluid or injected at the proposed site of infusion, (seefor example, “Remington's Pharmaceutical Sciences” 15th Edition, pages1035-1038 and 1570-1580). Some variation in dosage will necessarilyoccur depending on the condition of the subject being treated. Theperson responsible for administration will, in any event, determine theappropriate dose for the individual subject. Moreover, for humanadministration, preparations should meet sterility, pyrogenicity,general safety and purity standards as required by FDA Office ofBiologies standards,

In another aspect, the present invention provides a method of reducingor inhibiting RNA expression or activity in a cell. In such embodiments,the method comprises contacting the ceil with a modified oligonucleotide(or pharmaceutical composition thereof) having a chemistry patterndescribed herein, where the oligonucleotide hybridizes (e.g., is atleast substantially complementary to) an RNA transcript expressed by thecell. In some embodiments, the RNA is a miRNA.

In another aspect, the present invention provides a method of preventingor treating a condition in a subject associated with or mediated by RNAor expression thereof. In some embodiments, the RNA is a miRNA. Themethod of prevention or treatment according to the present inventioninvolves administering to the subject a pharmaceutical composition whichcomprises an effective amount of the base-modified oligonucleotide or aits pharmaceutically-acceptable composition thereof.

The invention provides a method for delivering the modifiedoligonucleotides to a mammalian cell (e.g., as part of a composition orformulation described herein), and methods for treating, ameliorating,or preventing the progression of a condition in a mammalian patient. Theoligonucleotide or pharmaceutical composition may be contacted in vitroor in vivo with a target cell (e.g., a mammalian cell). The cell may bea heart cell.

The method generally comprises administering the oligonucleotide orcomposition comprising the same to a mammalian patient or population oftarget cells. The oligonucleotide, as already described, may be a miRNAinhibitor (e.g., having a nucleotide sequence designed to inhibitexpression or activity of a miRNA). For example, where the miRNAinhibiter is an inhibitor of a miR-208 family miRNA, the patient mayhave a condition associated with, mediated by, or resulting from,miR-208 family expression. Such conditions include, for example, cardiachypertrophy, myocardial infarction, heart failure (e.g., congestiveheart failure), vascular damage, restenosis, or pathologic cardiacfibrosis, cancer, or other miRNA associated disorder, including thosedisorders described in the patent publication listed in Table 1. Thus,the invention provides a use of the modified oligonucleotides andcompositions of the invention for treating such conditions, and for thepreparation of medicaments for such treatments.

In certain embodiments, the patient (e.g., human patient) has one ormore risk factors including, for example, long standing uncontrolledhypertension, uncorrected valvular disease, chronic angina, recentmyocardial infarction, congestive heart failure, congenitalpredisposition to heart disease and pathological hypertrophy.Alternatively or in addition, the patient may have been diagnosed ashaving a. genetic predisposition to, for example, cardiac hypertrophy,or may have a familial history of, for example, cardiac hyper trophy.

In this aspect, the present invention may provide for an improvedexercise tolerance, reduced hospitalization, better quality of life,decreased morbidity, and/or decreased mortality in a patient with heartfailure or cardiac hypertrophy.

In certain embodiments, the activity of micoRNA in cardiac tissue, or asdetermined in patient serum, is reduced or inhibited.

In various embodiments, the pharmaceutical composition is administeredby parenteral administration or by direct injection into heart tissue.The parenteral administration may be intravenous, subcutaneous, orintramuscular. In some embodiments, the composition is administered byoral, transdermal, sustained release, controlled release, delayedrelease, suppository, catheter, or sublingual administration. In certainembodiments, the oligonucleotide is administered at, a dose of 25 mg/kgor less, or a dose of 10 mg/kg or less, or a dose of 5 mg/kg or less. Inthese embodiments, the oligonucleotide or composition may beadministered by intramuscular or subcutaneous injection, orintravenously.

In some embodiments, the methods further comprise scavenging or clearingthe miRNA inhibitors following treatment. For example, a oligonucleotidehaving a nucleotide sequence that is complementary to the inhibitor maybe administered after therapy to attenuate or stop the function of theinhibitor.

All references cited herein, including those in Table 1, are herebyincorporated by reference for all purposes.

EXAMPLES

Example 1

General Procedure For Preparation of 5-position-modified2′-O-methyhiridine nucleoside phosphoramidites

5-lodo-2′-O-methyluridine was readily synthesized by known methods, andis also commercially available. The 5′- and 3′-hydroxy 1 groups of thenucleoside are protected by standard 4,4′-Dimethoxytritylation andacetylation methods, respectively. This doubly protected nucleoside wasthen subjected to carboxamidation by dissolving the nucleoside in a 1:1mixture of anhydrous THF and N,N-dimethylacetamide in a 50 mLborosilicate boston round bottle. 5 equivalents of TEA and 3 equivalentsof a primary amine or amine hydrochloride were added to the mixturefollowed by addition of 0.1 equiv. oftetrakis(triphenylphosphine)palladium(0). The bottle was placed in a 300mL Parr Bomb fitted with a scalable inlet and pressure gauge. Theapparatus was flushed with carbon monoxide by charging to 60 psi withcarbon monoxide then releasing the pressure to 10 psi and repeatingtwice. The apparatus was then charged to 60 psi, sealed and placed in a70° C. oil bath for 17 h. The solvent was removed in vacuo, the residuere-dissolved in MeOH and de-acetylated at 55° C. under Zemplen orsimilar conditions. The resultant nucleoside was converted to thenucleoside phosphoramidite using the monochloridite method.

The 2′-deoxynucleosides can be synthesized in a similar manner asdescribed in Vaught et al., J. Am. Chem. Soc, 132(12):4141-4151 (2010)which are hereby incorporated by reference in their entireties.

Example 2 Preparation of5′-O-DMTr-3′-O-Ac-5-(2-(N4-methylpiperazinylethyl)carbamoyl)-2′-O-methyluridine (2c)

In a 50 mL Boston Round Bottle was 5′-O-DMTr-3′-O-Ac-5-IodoUridine (1 g,1.373 mmol) in THF (Volume: 10 ml) and DMA (Volume: 10 ml) to give acolorless solution. Tetrakis(triphenylphosphine)palladium(0) (0,159 g,0.137 mmol) is weighed out and added to the bottle followed by additionof triethyiamine (0.694 g, 6.86 mmol) and2-(4-methylpiperazin-1-yl)ethanamine (0.413 g, 2.88 mmol). The Bottle isplaced into a 250 mL Parr Bomb, which is sealed and evacuated throughthe needle valve. The Bomb is then pressurized to 60 psi with CarbonMonoxide. The bomb is then evacuated under high vacuum and re-chargedwith Carbon Monoxide (60 psi). The bomb is resealed and placed in an oilbath heated to 70° C. For 17 h. The bomb is cooled to it and thepressure released slowly. The bottle is removed from the bomb and thesolvent is removed in vacuo (Vaught et al., J. Am. Chem. Soc.,132(12):4141 -4151 (2010) which is hereby incorporated by reference inits entirety).

The dried product is re-dissolved in MeOH (10 mL) and 1 pellet of NaOH(˜40 mg) is added along with a small stir bar. The bottle is fitted witha septum and the mixture is stirred at 50° C. overnight. TLC (3% TEA inHexanes treated plate, 5% MeOH in DCM developing solvent, visualized viaUV and Hannessians Stain w/charring) reveals a single trityl bearingproduct. The reaction mixture is concentrated to dryness and applied toa 80 g ISCO silica cartridge that is equilibrated with DCM and 1% TEA.The product is eluted from the column with a 0-10% MeOH in DCM (1% TEA)solvent gradient over 2 L @ 60 ml/min. The pure fractions are collected,combined and concentrated to dryness to give 5′-O-DMTr-3′-O-Ac-5-(2-(N4-methylpiperazinylethyl)carboxamidoUridine (0.93g, 1.274 mmol, 93% yield) as a white foam. 1H NMR δ 2.33 (s, 3H),2.50-2.65 (m, 10H); 3.44-3.52 (m, 4H); 3.54 (s, 3H); 3.79 (s, 6H);3.87-3.92 (m, 1H); 4.00-4.08 (m, 1H); 4.10-4.17 (m, 1H); 5.90 (d, J=3.2Hz, 1H); 6.85 (dd, J=9.0, 1.3 Hz, 4H); 7.27-7.49 (m, 9H); 8.52 (s, 1H);8.77 (t, J=5.4 Hz, 1H). MS (ESI) M+1=730, calcd, 729.

Below are the experimental details for selected 5-carboxamido basemodifications shown in FIG. 2. Each compound was synthesized in the samemanner using the appropriate primary amine. All compounds gave yieldsbetween 60-95%.

Compound 2a, Propyl-imidazole derivative

Using 3 equivalents of 1-(3-aminopropyl)imidazole as the primary aminegave the desired product as an off white foam in 64% yield. ¹H NMR (300MHz) δ 2.00-2.10 (m, 2H); 3.21-3.37 (m, 2H), 3.46 (d, J=4.2 Hz, 2H),3.57 (s, 3H), 3.78 (s, 6H), 3.92 (dd, J=5.6, 3.2 Hz, 1H), 3.95-4.10 (m,4H), 4.15-4.22 (m, 1H), 5.92 (d, J=3.2 Hz, 1H), 6.08 (bs, 1H), 6.84 (dd,J=9.0, 1.4Hz, 4H), 6.93-7.50 (m, 10H), 7.63 (s, 1H), 7.76 (s, 1H), 8.58(s, 1H), 8.74 (t, J=6.0 Hz, 1H). MS (ESI+) calc'd 711.76, found 712.6.

Compound 2b, Propyl-morpholine derivative

Using 3 equivalents of 3-Morpholinopropylamine as the primary amine gavethe desired product as a white foam in 64% yield. ¹HNMR (300 MHz) δ 1.76(quin, J=7.0 Hz, 2H), 2.41-2.50 (m, 4H), 3.40-3.47 (m, 4H), 3.53 (s,3H), 3.70-3.75 (m, 8H), 3.79 (s, 6H), 3.89 (dd, .l 5.7, 3.2 Hz, 1H),3.98-4.15 (m, 2H), 5.90 (d, J=3.2Hz, 1H), 6.84 (dd, J=9.0, 0.9 Hz, 4H),7.15-7.48 (m, 9H), 8.48 (s, 1H), 8.75(t, J=5.8 Hz, 1H). MS (ESI+) calc'd730.8, found 731.5.

Compound 2e, Benzyl derivative

Using 3 equivalents of benzylamine as the primary amine gave the desiredproduct as a white foam in 87% yield. ¹HNMR (300 MHz) δ 3.45-3.49 (m,2H), 3.56 (s, 3H), 3.78 (s, 6H), 3.89 (dd, J=5.6, 3.1 Hz, 1H), 4.03-4.17(m, 2H), 4.58 (dd, J=5.7, 4.6 Hz, 2H), 5.90 (d, J=3.1 Hz, 1H), 6.85 (dd,J=9.0, 1.3Hz, 4H), 7.15-7.60 (m, 15 H), 8.59 (s, 1H), 8.87 (t, J=5.9 Hz,1H).

Compound 2h, 2-ethyl-N,N-dimethylamine derivative

Using 3 equivalents of N,N-dimethylethylenediamine as the primary aminegave the desired product as a white foam in 91% yield. ¹ HNMR (300 MHz)8 2.31 (s, 6H), 2.54 (t, J=6.5 Hz. 2H), 3.40-3.50 (m, 3H), 3.52 (s, 3H),3.79 (s, 6H), 3.88 (dd, J=5.6, 3.1 Hz), 3.95-4.10 (m, 4H), 5.86 (d,J=3.1Hz, 1H), 6.84 (dd, J=9.0, 1.4 Hz, 4H), 7.17-7.49 (m, 9H), 8.46 (s,1H), 8.79 (t, J=5.6 Hz, 1H).

Example 3 Preparation of5′-O-DMTr-5-((2-(N4-methylpiperazinylethyl)carbamoyl)-2′-O-methyhiridineAmidite (3c)

In a 100 mL round-bottomed flask was DIEA (0.364 ml, 2.084 mmol) and5-(3-(4-methylpiperazin-1-yl)propan-1-carboxamido)-5′-O-DMTr-3′-O-Ac-2′-O-Me-Uridine (1.55 g, 2.084mmol) dissolved in DCM (Volume: 15 ml) to give a colorless solution. Theflask was flushed with argon and set to stir.3-((chloro(diisopropylamino )phosphine)oxy)propanenitrile (or“monochloridite”) (0.451 g, 2.084 mmol) was added dropwise and thereaction mixture allowed to stir for 3 hours.

TLC revealed that the reaction was complete. The reaction mixture wasdiluted with sat NaHCO₃ (100 mL) and the aqueous phase was extractedwith DCM (3×50 mL). The organic phases were combined and dried with abrine wash (1×50 mL) and addition of Na₂SO₄. The organic phase wasfiltered and concentrated.

Purification was done via column chromatography on a 40 g silicacartridge pretreated with 3% TEA in Hexanes. Product was eluted with a0-5% MeOH in DCM (over 1L @ 40 mL/min). Pure fractions were combined andconcentrated to give a white amorphous foam. The product wasco-evaporated with DCM (3×30 mL) and dried under high vacuum overnightbefore use in automated oligonucleotide synthesis.5′-O-DMTr-5-((2-(N4-methylpiperazinyiethyl)carbamoyl)-2′-O-methyluridine Amidite (1.47 g, 1.557 mmol, 74.7% yield).1H NMR δ 1.15-1.25 (m, 12H): 2.31 (s, 3H); 2.36 (t, J=6.5 Hz, 2H);2.41-2.69 (m, 12H); 3.34-3.72 (m, 9H); 3.76-4.06 (m, 8H); 4.18-4.36 (m,1H); 5.90 (dd, J=5.4, 5.0 Hz, 1H); 6.80-6.92 (m, J=9.0, 4H); 7.15-7.51(m, 9H); 8.51 (ds, 1H); 8.78-8.90 (m, 1H). MS (ESI) M+1=931, calcd, 930.

Experimental details for selected 5-carboxamido base modifications inFIG. 2. Each compound was synthesized in the same manner using 1.00equivalents of 3-(((diisopropylamino)(methyl)phosphino)oxy)propanenitrile. All compounds gave yields between75-95%.

Compound 3b, Phosphoramidite of Propyl-morplioline derivative

White foam obtained in 82% yield after column chromatography(DCM/MeOH/TEA), A 1:1 mixture (determined by ¹H NMR) of diastereonierswas measured by NMR. The protons that were resolved are described beforethe tabulated results and denoted by an asterisk. ³¹P NMR (121.5 MHz) 5150.15*, 150.89*. In the proton spectra, the mixture gives rise to thefollowing resolved diastereomeric peaks: A singlet at 3.45 ppm* and 3.47ppm* corresponding to 3H of the 2′-O-methyl group; Two singlets at 3.80ppm* and 3.81 ppm* correspond to 6H of the methoxy groups on the trityl;two doublets at 5.92 ppm* and 5.96 ppm* with coupling constants of 5.0Hz and 5.4 Hz, respectively, and corresponding to 1H at theC1′-position; Two singlets at 8.49 ppm* and 8.56 ppm* corresponding to1H at the C-6 position of the base. The balance of peaks are as follows:¹H-NMR (300 MHz) δ 1.04-1.22 (m, 12H), 1.69-1.82 (m, 2H), 2.41-2.49 (m,6H), 2.58-2.67 (m, 2H), 3.33-3.44 (m, 4H), 3.51-3.65 (m, 3H), 3.70-3.76(m, 4H), 3.83-3.95 (m, 1H), 3.95-4.07 (m, 1H), 4.17-4.36 (m, 2H),6.82-6.89 (m, 4H), 7.15-7.51 (m, 9H), 8.63-8.76 (m, 1H). MS (ESI+)calc'd 931.0, found 931.8.

Compound 3a, Phosphoramidite of Propyl-imidazole derivative

White amorphous foam obtained in 80% yield after column chromatography(DCM/MeOH/TEA). A 55:45 mixture (determined by ¹H NMR) of diastereomerswas measured by NMR. The protons that were resolved are described beforethe tabulated results and denoted by an asterisk. ³¹P NMR (121.5 MHz) δ150.26*, 150.81*. In the proton spectra, the mixture gives rise to thefollowing resolved diastereomeric peaks: Two doublets of triplets withthe major diastereomer at at 2.63 ppm* (J=6.1, 1.3 Hz) and the minorsignal at 2.37 (J=6.3, 1.4 Hz) corresponding to 2H; Two singlets, bothat 3.49 ppm* correspond to 3H of the 2′-O-methyl groups; two doublets at5.92 ppm*(minor, J=4.5 Hz) and 5.99 ppm* (major, J=5.2 Hz) correspondingto 1H at the C1′-position; Two singlets at 8.55 ppm* (major) and 8.63ppm* (minor) corresponding to 1H at the C-6 position of the base. Thebalance of peaks are as follows: ¹H-NMR (300 MHz) δ 1.04-1.22 (m, 12H),1.97-2.10 (m, 2H), 2.80-2.94 (m, 1H), 3.23-3.47 (m, 4H), 3.52-3.74 (m,3H), 3.75-3.95 (m, 7H), 3.96-4.13 (m, 3H), 4.22-4.41 (m, 2H), 6.79-6.89(m, 4H), 6.96 (s, 1H), 7.10 (s, 1H), 7.15-7.53 (m, 9H), 7.59 (s, 1H),8.69-8.80 (m, 1H). MS (ESI+) calc'd 912.0, found 912.3.

Compound 3h, Phosphoramidite of 2-ethyl-N,N-dimet,hylamine derivative

White amorphous foam, obtained in 87% yield after column chromatography(DCM/MeOH/TEA). A 55:45 mixture (determined by ¹H NMR) of diastereomerswas measured by NMR. The protons that were resolved are described beforethe tabulated results and denoted by an asterisk. ³¹P NMR (121.5 MHz) δ150.12*, 150.71*. In the proton spectra, the mixture gives rise to thefollowing resolved diastereomeric peaks: two doublets at 5.90 ppm*(minor, J=4.8 Hz) and 5.93 ppm* (major, J=5.2 Hz) corresponding to 1H atthe C1′-position; Two singlets at 8.46 ppm* (major) and 8.53 ppm*(minor) corresponding to 1H at, the C-6 position of the base. Thebalance of peaks are as follows: ¹H-NMR (300 MHz) δ 1.04-1.22 (m, 12H),2.31 (s, 6H), 2.52-3.06 (m, 4H), 3.33-3.49 (m, 5H), 3.52-3.74 (m, 4H),3.75-3.94 (m, 7H), 3.95-4.07 (m, 1H), 4.16-4.34 (m, 2H), 6.80-6.90 (m,4H), 7.15-7.53 (m, 10H), 8.68-8.82 (m, 1H).

Compound 3e, Phosphoramidite of Benzyl derivative

White amorphous foam obtained in 89% yield after column chromatography(EtOAc/Hex). A 55:45 mixture (determined by ¹H NMR) of diastereomers wasmeasured by NMR. The protons that were resolved are described before thetabulated results and denoted by an asterisk. ³¹ P NMR (121.5 MHz) δ150.26*, 150.81*. In the proton spectra, the mixture gives rise to thefollowing resolved diastereomeric peaks: Two doublets of triplets withthe major diastereomer at at 2.64 ppm* (J=6.5, 2.1 Hz) and the minorsignal at 2.38 (J=6.5, 1.5 Hz) corresponding to 2H; Two doublets at 5.93ppm*(minor, J=4.7 Hz) and 5.98 ppm* (major, J=5.3 Hz) corresponding to1H at the C1′-position; Two singlets at 8.57 ppm* (major) and 8.64 ppm*(minor) corresponding to 1H at the C-6 position of the base. The balanceof peaks are as follows: ¹H-NMR (300 MHz) δ 1.04-1.22 (m, 12H),3.36-3.46 (m, 2H), 3.50-3.76 (m, 4H), 3.77-3.93 (m, 7H), 3.95-4.10 (m,1H), 4.17-4.36 (m, 2H), 4.45-4.67 (m, 2H), 6.82-6.90 (m, 4H), 7.15-7.54(m, 14H), 8.83-8.95 (m, 1H). MS (ESI+) calc'd 912.0, found 912.3.

Example 4 General Synthetic Methodology of Truncated Nucleotides

Carboxamido-substituents for modifications were chosen from bothhydrophilic and hydrophobic groups. Hydrophilic groups werepreferentially chosen for the following reasons: Their ability to createnew hydrogen bonding interactions with other nucleobases; the lack ofexchangeable protons or sensitive functional groups that would requireextra protecting groups under standard oligonucleotide synthesis; thecationic nature of these groups at physiological pH. Hydrophobic groupswere chosen to attempt to exploit pi-stacking interactions betweennucleobases and to create new hydrophobic regions in the nucleotide.Creating new hydrophobic and cationic/hydrophilic regions on anucleotide may also create enhanced binding to serum proteins thatenhance cell permeability. Pendant hydrophobic groups (such as sterolsand straight chain lipids) as well as nucleotides with 2′-hydrophobicmodifications (such as alkyl, aryl and 2′-4′-linkers) can enhancecellular uptake by increasing interaction with serum lipoproteinparticles. Likewise, counteracting the very anionic nucleotide backbonewith highly charged cationic species also enhances cellular uptake.

Short strands of oligonucleotides bearing sugar and base modificationscan be prepared once the modified nucleoside is synthesized and the free5′ and 3′-hydroxyl groups are masked with appropriate reactive groups tobecome a nucleotide monomer. The current state of the art inoligonucleotide synthesis is automated solid phase synthesis usingphosphoramidite chemistry, which, in particular, is based on thedevelopments of McBride et al., Tetrahedron Letters 24:245-248 (1983)and Sinha et al., Tetrahedron Letters 24:5843-5846 (1983).Phosphoramidite chemistry, together with related methods such ashydrogen phosphonate chemistry, has been extensively reviewed withrespect to their uses in oligonucleotide chemistry by Beaucage et al.,Tetrahedron 48:2223-2311(1992). During solid phase oligonucleotidesynthesis, a series of nucleotide monomers are sequentially attached,via their phosphoramidite derivatives, in a predetermined order toeither, depending on the direction of chain extension, the 5′-functionalgroup or the 3′-functional group of the growing oligonucleotide strand.

The oligonucleotide strand is anchored to an insoluble moiety such ascontrolled pore glass or polystyrene resin beads. The method ofattachment of each monomer is generally comprised of the following steps1-5. Step 1 involves the protection of the reactive functionality. Thecommon reactive functionality is the 5′-hydroxyl group of the terminalnucleoside. This functionality is usually protected with a4,4′-dimethoxytrityl (DMT) moiety that can be removed via acidtreatment. One of the attractive features of the DMT moiety is that itforms a bright orange DMT cation during acid deprotection. This cationserves effectively as reporter group that can be easily monitored at awavelength between 480 and 500 nm for the purpose of judging thecompleteness the previous coupling step. Most commercially availableautomated synthesizers have the capability to monitor the released DMTcation. This data gives the operator an instant indication of whether ornot the synthesis failed at any given step. Step 2 involves the couplingby addition of a phosphoramidite derivative and an activator. Thephosphoramidite derivative is usually a nucleoside phosphoramidite,however, it may also be a phosphoramidite derivatized with a differentorganic moiety. Step 3 involves the capping of unreacted terminalfunctional groups. This step introduces an inert protective group thatprevents further coupling to failure sequences. Step 4 involvesoxidation of the newly formed phosphorous nucleotide backbone linkagefrom the trivalent phosphite to the stable pentavalent state. Thisoxidation step can be performed with either an oxygen-based oxidant thatresults in a phosphate nucleotide or a sulfurizing oxidant that resultsin a phosphorothioate nucleotide. Step 5 involves a repetition of theprocess the after a washing step.

Truncated, 16 nucleotide sequence complementary to a nucleotide sequenceof human miR-208a was synthesized in 1 μmol scale on an ABI Expedite8909 Automated Nucleic Acid Synthesis System, The synthesizer wasoperated using standard detritylation and capping solutions, known tothose skilled in the art, single couplings of 420 seconds for each baseand oxidation with 0.2M PADS oxidation solution after each couplingcycle. The unmodified anti-208a RNA sequence incorporates nine uridineresidues which were fully replaced with nine modified nucleobases. Thebalance of the nucleotides were comprised of 2′-O-methyl-nucleotides.One exception was the incorporation of oleylcarboxamido derivative,where there is a single incorporation on base position 15 of 16 wherethe nucleoside amidite was incorporated via a double coupling of 420seconds each.

Example 5 Preparation of Oligonucleotide miRNA Inhibitors

Preparation of compound10941(mCs;ppTs;ppTs;ppTs;ppTs;ppTs;mGs;mCs;ppTs;mCs;mGs;ppTs;mCs;ppTs;ppTs;mA).Phosphoramidite Reagent (3c) in the Synthesis of the Base ModifiedOligonucleotide was used. The oligodeoxynucleotide was synthesized usingan ABI Expedite (Model 8909) DNA/RNA synthesizer. The synthesis wasperformed according to the manufacturer's recommendations in DMT-ON modeemploying commercial synthesis reagents, exchanging 0.2M PADS in 1:1Pyridine/ACN for the oxidizing solution. The phosphoramidite reagent wasadded as a 0.1 M solution in acetonitrile during the appropriatecoupling cycle. The cleavage of the oligonucleotide from the support wasaccomplished either by the method of described in U.S. Pat. No.5,750,672 (which is hereby incorporated by reference in its entirety) orvia heating of the CPG bound oligonucleotide with a solution of 40%aqueous methyl amine at 55° C. for 30 minutes. The resultant aqueoussolution of oligonucleotide was further purified by loading the crudeDMT-ON oligonucleotide solution on a Waters Sep-Pak® Vac C18 cartridgeand eluting using a standard DMT-ON oligonucleotide desalting procedureknown to those knowledgeable in the art. The characterization of productwas performed by MALDI-TOF mass spectrometry utilizing3-hydroxypicolinic acid as matrix and standard methods known to thoseknowledgeable in the art: calcd 6922.4, found 6920.7.

Compound M-10708 (FIG. 5) was synthesized with amidite 3e in the uridineposition in exactly the manner described above. The characterization ofproduct was performed by ESI mass spectrometry on a Waters SQD massdetector in 200 mM HFIP/8.15 mM TEA buffer gradient with MeOH: calcd6597.6, found 6599.1.

Compound M-10713 (FIG. 5) was synthesized with amidite 3f in the uridineposition in exactly the manner described above. The characterization ofproduct was performed by ESI mass spectrometry on a Waters SQD massdetector in 200 mM HFIP/8.15 mM TEA buffer gradient with MeOH: calcd6543.9, found 6543.9.

Compound M-10711 (FIG. 5) was synthesized with amidite 3a in the uridineposition in exactly the manner described above. The characterization ofproduct was performed by ESI mass spectrometry (negative mode) on aWaters SQD mass detector in 200 mM HFIP/8.15 mM TEA buffer gradient withMeOH: calcd 6759.8, found 6759.6.

Compound M-10712 (FIG. 5) was synthesized with amidite 3d in the uridineposition in exactly the manner described above. The characterization ofproduct was performed by ESI mass spectrometry (negative mode) on aWaters SQD mass detector in 200 mM HFIP/8.15 mM TEA buffer gradient withMeOH: calcd 6759.8, found 6760.6.

Compound M-10768 (FIG. 5) was synthesized with 2′-O-methyluridine in itsamidite position and amidite 3d in the auxiliary amidite position inexactly the manner described above. The characterization of product wasperformed by ESI mass spectrometry (negative mode) on a Waters SQD massdetector in 200 mM HFIP/8.15 mM TEA buffer gradient with MeOH: calcd6003.9, found 6005.2.

Compound M-10772 (FIG. 5) was synthesized with amidite 3i in the uridineposition in exactly the manner described above. The characterization ofproduct was performed by ESI mass spectrometry (negative mode) on aWaters SQD mass detector in 200 mM HFIP/8.15 mM TEA buffer gradient withMeOH: calcd 6552.8, found 6553,4.

Compound M-10774 (FIG. 5) was synthesized with 2′-O-methyluridine in itsamidite position and amidite 3i in the auxiliary amidite position inexactly the manner described above. The characterization of product wasperformed by ESI mass spectrometry (negative mode) on a Waters SQL) massdetector in 200 mM HFIP/8.15 mM TEA buffer gradient with MeOH: calcd5912.0, found 5912.8.

Compound M-10876 (FIG. 5) was synthesized with amidite 3b in the uridineposition in exactly the manner described above. The characterization ofproduct was performed by ESI mass spectrometry (negative mode) on aWaters SQD mass detector in 200 mM HFIP/8.15 mM TEA buffer gradient withMeOH: calcd 6931.2, found 6931.9.

Compound M-10877 (FIG. 5) was synthesized with amidite 3b in the uridineposition and amidite 3g in an auxiliary amidite position on the ABIExpedite (Model 8909) DNA/RNA synthesizer. The oligonucleotide washandled in exactly the manner described above, except amidite 3g was thefirst coupling to 2′-O-Me-adenosine functionalized CPG, Incorporation of3g is denoted by the precursor “y” in FIG. 5. The characterization ofproduct was performed by ESI mass spectrometry (negative mode) on aWaters SQD mass detector in 200 mM HFIP/8.15 mM TEA buffer gradient withMeOH: calcd 7056.0, found 7056.5.

Compound M-10878 (FIG. 5) was synthesized with 2′-O-methyluridine in itsamidite position and amidite 3b in the auxiliary amidite position inexactly the manner described above. The characterization of product wasperformed by ESI mass spectrometry (negative mode) on a Waters SQD massdetector in 200 mM HFIP/8.15 mM TEA buffer gradient with MeOH: calcd6080.1, found 6081.

Compound M-10881 (FIG. 5) was synthesized with 2′-O-methyluridine in itsamidite position and amidite 3b in the auxiliary amidite position inexactly the manner described above. The characterization of product wasperformed by ESI mass spectrometry (negative mode) on a Waters SQD massdetector in 200 mM HFIP/8.15 mM TEA buffer gradient with MeOH: calcd6250.3, found 6251.5.

Example 6 Determination of Melting Temperature

Melting temperature (T_(m)) enhancement was determined on a perincorporation basis by determining the difference between the meltingtemperature of the modified strand and that of the identical sequenceutilizing either a phosphorothioate DNA nucleotide or a phosphorothioate2′-O-methyl RNA nucleotide.

For example, the modified anti-208a oligonucleotides were annealed tothe complementary sequence, twenty-two nucleotides in length, comprisedof RNA nucleosides and a phosphate backbone. The complementary sequencewas identical to the endogenous miRNA. Thermal denaturation temperatures(T_(m)) were measured as a maximum of the first derivative plot ofmelting curvex (A260 vs. Temp). The duplexes were constituted at 1 μM ina 0.9% NaCl buffer. Temperature was ramped from 25° C. to 95° C. at 4°C./min and OD's at 260 nm were read once per minute, T_(m) values areaverages of at least two measurements.

Duplex melting temperatures for various modifications of a 16 nucleotidesequence complementary to a nucleotide sequence of human miR-208a.Modifications included a mixed 9 LNA/7 DNA phosphorothioate, fullysubstituted 2′-O-methyl-nucleotide phosphorothioate, fully2′-deoxynucleotide phosphorothioate and various substitution patterns offully 2′-O-methyl-nucleotides with 5-carboxamide substituents. Whilehydrophobic substitutions did not provide substantial gains in affinityenhancement versus the unmodified 2′-O-methyl parent compound, all ofthe cationic species provided significant duplex stabilization on theorder of 2-3° C./Modification over the unmodified 2′-OMe nucleotide.Duplexes were constituted at 1 μM in 0.9% NaCl. Temperature was rampedfrom 25° C. to 95° C. at 4° C./min and OD's at 260 nm were read once perminute on a Cary 100 Bio UV-Visible Spectrophotometer. See FIG. 4 andFIG. 5.

Example 7 Cardiomyocytes Data

Cell culture experiments conducted with primary neonatal ratcardiomyocytes demonstrate that many of the 5-carboxamido-base modifiedoligonucleotides not only bind to miR-208a, but also effect thedownstream regulation of bMHC in a manner expected for effective,intracellular miR-208a inhibitors. As shown in FIGS. 6 and 7, two knownpositive controls that contain LNA/DNA or LNA/2′-O-Me mixtures ofnucleotides show both miR-208a inhibition and a dose dependentregulation of bMHC. All oligonucleotides were passively (no transfectionreagent) put onto the cells in 2% serum containing media. The cells werelysed using Cells to Ct (Ambion) buffer after 72 hour incubation at 37°C. MiR-208a and the mRNA bMHC were analyzed by Taqman based RT-PCR(Applied Biosystems). All experiments were performed in triplicate andshown as average +/−standard deviation. Base modifications that featurependant cationic species with pKa values in the 7-8 range, those mostlikely to be mostly protonated at physiological pH, were more likely toshow a positive correlation between miR-208a inhibition and bMHC. Thiscorrelation suggests that the miR-208a inhibition occurs pre-lysis ofthe primary cardiomyocytes. It should also be noted that nucleotidesubstitution patterns can affect the potency of inhibitors having thesame sequence. The 5-(2-(2-methyl-1H-imidazol-1-yl)-ethylcarboxamido)-2′-O-methyluridine nucleotide variant showsinhibition of miR-208a when incorporated in a 16-nucleotide 2′-O-methylphosphorothioate anti-208a nucleotide sequence where either 4 or 9 ofthe total 9 natural uridine nucleotide positions are substituted. It isonly the oligonucleotide that has 4 substitutions that shows effectivebMHC mRNA regulation.

Example 8 In Vivo Testing

Three base modified oligonucleotides were studied in vivo in C57BL/6mice (10941, 10876, 10711). A scrambled control containing thecomparable bases of each oligo were also injected (11091, 11087, 11086).The oligonucleotides were dosed with a 25 mg/kg delivered viasubcutaneous injection on Day I. Cardiac tissue was harvested 4daysafter dosing and miR-208a levels were determined via. real time PCR.There was neither injection site reaction nor any visible organ damagefollowing take down of the mice. As seen in FIG. 8, all targeting oligosshowed some inhibition of miR-208a, and the 10711 oligonucleotide wasable to inhibit miR 208a, in cardiac tissue in a statisticallysignificant, manner compared to saline. None of the controls werestatistically different than saline. This demonstrated the ability ofsystemically administered base modified oligonucleotides to act aspotent inhibitors of cardiac specific miRNA's without the use ofconjugates or drug delivery systems.

Example 9 T_(m) Differences Between 2′-deoxy and 2′-O-Me BaseModifications

T_(m) effects of both base and sugar modifications when visualized on ascale from least modified to most modified. Base modifications alone areexpected to have only a modest effect on 2′-deoxyribonucleosides withphosphate backbones (see examples of Ahmadian et al., Nucleic AcidsRes., 1998, 26(13):3127-3135 (1998); Znosko et al., J. Am. Chem. Soc.,125(20):6090-6097 (2003) which are hereby incorporated by reference intheir entireties), and even then, substituents larger than C3-alkynestend to destabilize DNA:DNA duplex stabilities. Even multipleincorporations of uridine based nucleosides with non-caxboxamido-linkedhexylamines, protonated under physiological pH, showed no net DNA:DNAduplex stabilization (see Hashimoto et al., J, Am. Chem. Soc.,115(16):7128-7134 (1993) which is hereby incorporated by reference inits entirety). Sugar modifications, in this case, 2′-O-methylatedribonucleosides, have been shown in our hands to stabilize thisparticular duplex with miR-208a RNA at about 1° C./modification. The2′-deoxynucleosides with base modifications taught in this invention,when fully incorporated (9-substitutions for uridine) in a 16-mer,anti-208a oligonucleotide with a phosphorothioate backbone, give littleincreased duplex stabilization against miR-208a RNA. See FIG. 9.However, when the base modified 2′-deoxynucleosides were incorporatedinto a nucleotide that also contained 2′-O-methylated nucleosides forall bases excluding uridine, the stabilization of the base modificationbecame apparent. Even though there were nine fewer sugar modifications,the duplex had the same Tm as the oligonucleotide with sixteen2′-O-methyl sugar modifications. 2′-O-Methylated anti-208a substitutingeach uridine with a uridine-based nucleoside that have both a5-carboxamido-base modification and a 2′-O-methyl sugar modificationshow an unexpected increase in Tm of more than 2° C./modification overthe oligonucleotide with just sugar modifications.

These enhanced affinities likely are greatest when coupled with A-formnucleosides that have a 3′-endo sugar pucker. This effect may be morepronounced when the 5-carboxamido modified base is combined with2′-4′-bridged bicyclic nucleoside sugar that locks the ribose in theA-form with a pronounced 3′-endo sugar pucker.

Example 10 Synergistic Effect of 5-Carboxamido- and 2′-O-MethylModifications is the Nucleotide.

FIG. 10 presents data from FIG. 9 as ΔT_(m)/per modification, countingboth sugar and base modifications. Multiple incorporations of5-carboxyamido-2′-O-methyluridine nucleosides unexpectedly give agreater stabilization per sugar and base modification than either thebase or sugar do alone. This evidence indicates that 5-carboxamido inconjunction with modifications that favor a 3′-endo sugar pucker ofnucleosides are more than additive. They work synergistically to givegreater duplex stability than either modification alone. Increasedduplex stability, subject to limits, is likely desirable for certainoligonucleotide based therapeutics, such as microRNA inhibitors.Furthermore, these types of modifications may also protect fromenzymatic degradation, cellular delivery due to decreased electrostaticcharge and enhanced pharmacokinetic and/or pharmacodynamic properties.

Example 11 Effect of Multiple Incorporations of Base ModifiedNucleotides in the Oligonucleotide

Multiple incorporations (i.e. 9 bases out of 16 total) of a cationic5-carboxamido-modified cleoxyuridine seems to give minimal boosts toduplex stability for both phosphorothioate and phosphate backbone 16-meroligonucleotides. See FIG. 11. This may be due to perturbations inhydrating the bases or steric bulk of the substituents. It is surprisingto note, though, that a single incorporation can increase the duplexstability of a 16-mer anti-208a deoxyoligonucleotide with eitherphosphorothioate or phosphate backbones with its target, miR-208a RNA,by more than 10° C. and 17° C., respectively. The modificationsdisclosed in this invention can be used alone, as single or multipleincorporations, or in conjunction with other sugar modifications, assingle or multiple incorporations, to obtain a therapeuticoligonucleotide with desirable duplexing properties, duplex-proteinbinding properties, or along with desirable pharmacokinetic and/orpharmacodynamic properties.

Although preferred embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions, substitutions, and the like canbe made without departing from the spirit of the invention and these aretherefore considered within the scope of the present invention asdefined in the claims which follow.

1. An oligonucleotide comprising at least one nucleotide having a 2′modification and at least one nucleotide having an amino carbonylmodified base.
 2. The oligonucleotide of claim 1, wherein theoligonucleotide hybridizes to a human microRNA with high affinity. 3.The oligonucleotide of claim 1, wherein the oligonucleotide is fromabout 6 to about 22 nucleotides in length.
 4. The oligonucleotide ofclaim 3, wherein the oligonucleotide is from about 10 to about 18nucleotides in length.
 5. The oligonucleotide of claim 1, wherein eachamino carbonyl group is independently selected from a carboxamino, acarbamoyl, or a carbamide group.
 6. The oligonucleotide of claim 5,wherein the base is modified at C-5 for pyrimidine or C-8 for purine. 7.The oligonucleotide of claim 5, wherein the base modification is acarboxamino group.
 8. The oligonucleotide of claim 1, wherein the basemodification contains a substituent selected from C₁-C₁₈ alkyl, C₁-C₁₈alkenyl, cycloalkyl, aryl, heterorayl, heterocyclyl, and—(CH₂)_(n)-NR₁R₂, wherein n is an integer from 1 to 6 and R₁ and R₂ areindependently H or C₁-C₆alkyl.
 9. The oligonucleotide of claim 1,wherein the base modification contains a pendent lipophilic substituent.10. The oligonucleotide of claim 1, wherein the base modificationcontains a pendent hydrophilic substituent. 11-13. (canceled)
 14. Theoligonucleotide of claim 1, wherein the 2′ modification is a 2′-4′bridge locking the sugar in the C3 endo configuration.
 15. (canceled)16. The oligonucleotide of claim 1, wherein the 2′ modification is 2′O-alkyl(C1-C6), F, Cl, NH₂, CN, or SH.
 17. The oligonucleotide of claim1, comprising 2 or more nucleotides with a 2′ modification, and 2 ormore nucleotides having the base modification, the 2′ modificationsbeing independently selected from 2′O-alkyl(C1-C6), F, Cl, NH₂, CN, SH,and a 2′-4′ bridge locking the sugar in the C3 endo configuration.18-19. (canceled)
 20. The oligonucleotide of claim 1, having from 2 toabout 10 nucleotides having both the 2′ modification and the aminocarbonyl modified base. 21-26. (canceled)
 27. The oligonucleotide ofclaim 1, wherein the oligonucleotide has one or more 2′ deoxynucleotides. 28-29. (canceled)
 30. The oligonucleotide of claim 1,having a 5′ and/or 3′ cap structure.
 31. The oligonucleotide of claim 1,containing one or more phosphorothioate linkages. 32-33. (canceled) 34.The oligonucleotide of claim 1, wherein the nucleotide sequence issubstantially complementary to a sequence of miR-208a, miR-208b,miR-15b, or miR-21.
 35. The oligonucleotide of claim 1, wherein thenucleotide sequence is substantially complementary to a sequence of ahuman miRNA listed in Table
 1. 36. (canceled)
 37. A pharmaceuticalcomposition comprising an effective amount of the oligonucleotide ofclaim 1, or a pharmaceutically-acceptable salt thereof, and apharmaceutically-acceptable carrier or diluent.
 38. (canceled)
 39. Amethod of reducing or inhibiting microRNA activity in a cell comprisingcontacting the cell with the oligonucleotide of claim
 1. 40-42.(canceled)
 43. A method of preventing or treating a condition in asubject associated with or mediated by expression of a microRNA,comprising administering to the subject the pharmaceutical compositionof claim
 37. 44-49. (canceled)